A divided US Supreme Court decided Saturday morning to allow Texas officials to continue to enforce the state’s voter identification law, despite a federal judge’s ruling a week ago that the law was discriminatory and amounted to an unconstitutional poll tax.

The justices split 6 to 3 on the issue. The order, announced shortly after 5 a.m., means that Texas voters will have to show photo identification before being allowed to cast a ballot in the mid-term elections.

Early voting is set to begin in Texas on Monday in advance of the Nov. 4 elections.

In a sharply worded dissent, Justice Ruth Bader Ginsburg cited the ruling last week by a federal judge in Corpus Christi, who found that the voter ID law was unconstitutional and threatened to “disenfranchise” up to 600,000 registered Texas voters who are believed to lack the required form of identification.

“The greatest threat to public confidence in elections in this case is the prospect of enforcing a purposefully discriminatory law, one that likely imposes an unconstitutional poll tax and risks denying the right to vote to hundreds of thousands of eligible voters,” Justice Ginsburg wrote in a seven-page dissent joined by Justices Sonia Sotomayor and Elena Kagan.

The high court action stems from a decision issued by US District Judge Nelva Gonzales Ramos after a two-week trial.

The judge, an appointee of President Obama, ruled that the state’s Republican-controlled legislature enacted the voter ID law with the intent to discriminate against African-American and Latino voters who disproportionately lack one of seven forms of acceptable ID.

She said the photo identification requirement amounted to an unconstitutional poll tax since it could cost those seeking new IDs anywhere from $2 to $37 in document fees.

Judge Gonzales Ramos ordered the state to revert to a more relaxed identification protocol used before the photo ID measure took effect in June 2013.

The tougher photo ID requirement has been used in the last three statewide elections.

In a brief to the Supreme Court, Texas Solicitor General Jonathan Mitchell said the judge’s findings concerning racial motive and discrimination were “preposterous.”

He said the estimate that 600,000 registered voters would be disenfranchised was “concocted” through an uncritical comparison of databases that included new registered voters but did not eliminate registrants who died or moved out of state.

State officials complained that the federal judge’s ruling, issued within days of an approaching election, would result in confusion at the polls.

A panel of the New Orleans-based Fifth US Circuit Court of Appeals agreed and issued a stay on Tuesday that would allow the photo ID law to remain in effect.

They argued that the safest approach to avoid voter confusion would be to allow Texas voters to cast ballots under the state’s old identification protocol.

On Saturday, the high court rejected that approach.

The issue of state-enacted changes to voting procedures has been on the high court’s radar in recent weeks, with the justices being asked to block or uphold election changes in three different cases in Ohio, North Carolina, and Wisconsin.

Of the high court’s actions in the three cases, two supported Republican-favored outcomes, while the third supported the position of Democrats.

On Oct. 9, the court blocked enforcement of a Wisconsin voter ID law that was opposed by Democrats but had been upheld by a federal appeals court. On Oct. 1, the justices permitted full enforcement of Republican-backed changes to North Carolina’s election regulations, including eliminating same-day registration and prohibiting the counting of ballots cast in the wrong precinct. And on Sept. 24, the court upheld enforcement of a Republican-backed law in Ohio that reduced early voting hours in that state.

The stakes in the Texas voter ID case extend far beyond what voters will have to show to cast a ballot in the coming elections. If Gonzales Ramos’ decision is upheld on appeal, it would force Texas to submit all future election changes to the Justice Department or a three-judge panel for pre-approval.

That pre-approval requirement disappeared after the Supreme Court in June 2013 invalidated that portion of the Voting Rights Act. A three-judge panel had earlier ruled against the Texas ID law, finding that it imposed a disproportionate burden on minority and elderly voters.

After the high court narrowed the scope of the Voting Rights Act, the earlier decision no longer applied. Texas moved to enforce the new voter ID law.

Various groups sued to have the ID law, once again, declared invalid.

Gonzales Ramos’ ruling includes a finding that the state violated the Voting Rights Act by passing a law that was discriminatory in both purpose and effect. She said it would be disproportionately harder for African-American and Latino voters to obtain compliant ID.

In her dissent, Ginsburg said the high court’s recent actions in the Ohio and North Carolina election law cases were different than the Texas case. In Texas, a federal judge had conducted a full trial and compiled an extensive record from which the judge found “ballot-access discrimination by the state,” she said.

The appeals court should have shown deference to the judge’s findings and blocked the ID law from being enforced in the current elections, she said.

Requiring voters to show photo ID before casting a ballot has become a divisive political issue. Democrats generally oppose such measures, saying they make it harder for minority and elderly voters. Republicans generally favor such measures, arguing that showing ID helps protect the integrity of elections and boosts public confidence in the outcome.

While many states require some form of identification to vote, only seven will enforce a strict photo ID requirement during this year’s mid-term elections, according to the National Conference of State Legislatures.

The seven states are Georgia, Indiana, Kansas, Mississippi, Tennessee, Virginia, and Texas.

Both Pennsylvania and Arkansas had strict photo ID laws that were overturned in the courts. Wisconsin’s photo ID law has been upheld by a federal appeals court, but it was blocked by the US Supreme Court from being used in the November elections.

North Carolina also has a photo identification requirement in its election law, but it does not take effect until 2016.